Carboxylic Acids Flashcards Preview

Organic chemistry and synthesis A2 > Carboxylic Acids > Flashcards

Flashcards in Carboxylic Acids Deck (18):

EsterAcid hydrolysis
What it forms

Heat with aqueous acid HCl

Forms a carboxylic acid and alcohol

Eater + water ---> (H+/heat) acid + alcohol


Converting carboxylic Acids to acid chlorides

Reflux with either phosphorus pentachloride PCl5 or sulfur dichloride oxide SOCl2

NUCLEOPHILIC substitution

Anhydrous conditions- because otherwise the acid chloride will hydrolyse back to the acid


What are the products in making acid chlorides using phosphorus pentachloride?

Acid chloride




What are the products in converting acid chlorides with sulfur dichloride oxide SOCl2

Acid chloride




Why is SOCL2 preferred when converting carboxylic acids to acid chlorides?

Because only gaseous co-products are formed. The product in PCl5 (POCl3) is a liquid which means you'd have to separate the acid chloride which is also a liquid- this would be difficult


Ester Alkaline hydrolysis

Heat with NaOH (aq)
Forms sodium salt of acid and alcohol

2- obtain a Carboxylic acid by adding strong hydrochloric acid to the sodium salt as sodium salts are fairly soluble


Hydrolysis of acid chlorides

What happens when ethanoyl chloride is opened?

They produce carboxylic acids

NUCLEOPHILIC substitution

When ethanoyl chloride is opened - misty fumes of HCl is seen- it reacts wth water vapour in the air


How soluble are aliphatic acids?

Fairly soluble in water eg ethanoic


How soluble are aromatic acids in water?

Sparingly soluble e.g benzoicacid


How to form a aromatic carboxylic acid from a. Sodium salt?

Treat sodium salt of benzoicacid with HCl and the benzoicacid will precipitate out of solution as ts sparingly soluble


How do isolate the product?

Filter product
Wash with cold solvent water
Recrystallise from hot water
Dry crystals in oven just below MP


How are aromatic carboxylic acids formed?

Acids are produced by the oxidisation of a side chain of an aromatic compound. Aromatic compound is heated with aqueous alkaline KMnO4 where the alkali is Na2CO3

This produces a sodium salt of the acid

Salt is then acidified with hydrochloric acid to produce the aromatic acid


Reagent used in the formation of aromatic carboxylic acids

And conditions

Aqueous alkaline potassium manganate (VII)

(Use HCl to acidify salt)

Condition: heat


Steps of forming aromatic carboxylic acids

Aromatic compound
(Alkaline aqueous KMnO4 + heat)

Sodium salt produced of the carboxylic acid

(HCl) acidified salt

Aromatic acid formed


Method of decarboxylation

1. React carboxylic acid with aqueous sodium hydroxide which forms sodium salt

2. Heat sodium salt with soda lime (NaOH)

3.hydrocarbon formed with 1 less C

4. Carbon dioxide gas isn't evolved

Mass spec can be used to identify the hydrocarbon and hence the patent carboxylic acid


Reaction equation for the acid hydrolysis of an ester

Water + water ---> (Heat/H+) carboxylic acid and alcohol


Reaction equation for the acid hydrolysis of an ester

Water + water ---> (Heat/H+) carboxylic acid and alcohol


Describe the solubility of aromatic and aliphatic acids

Aromatic acids are sparingly soluble in water always, eg barely dissolves, aliphatic acids are fairly soluble in water always - dissolves